quiz4d - site. 2. GABA binds to both B and M receptor...

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Quiz 4d – Apopka True/False (2 pts. each) You have shown that the following drugs all can affect seizure threshold in rats: GABA, THIP, muscimol, glutamate and Drug X, but baclofen did not change seizure threshold at any concentration (see Figure 1 below). You have also measured and compared the efficacies and potencies of these drugs to displace the specific binding of 3 H-GABA from homogenized brain samples. Only 70% of the receptors occupied by 3 H-GABA bind muscimol (Subtype M) while only 30% of the receptors bind baclofen (Subtype B). Which of the following conclusions are true after examining the resulting competition curves shown in Figure 2? If you don’t have any evidence to prove that the statement is true, then answer false. 1. Drug X has a higher affinity for the "M" site compared to THIP’s affinity for the “M”
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Unformatted text preview: site. 2. GABA binds to both B and M receptor subtypes but baclofen does not. 3. The IC 50 values for GABA to bind to the two subtypes must be very different (more than 100-fold different). 4. Agonists for the "M" subtype appear to increase seizure thresholds in rats by positively activating that receptor subtype. 5. Drug X is an inverse agonist at B receptors. 6. THIP is a partial agonist at M receptors. 7. Glutamate is an inverse agonist for the "M" subtype. Figure 1. Figure 2. 20 40 60 80 0.01 0.03 0.1 0.3 1 3 10 30 100 300 1000 3000 Drug Dose (mg) Seizure threshold (nAmps) muscimol GABA Glu. X Baclofen THIP 10 20 30 40 50 60 70 80 90 100 0.01 0.03 0.1 0.3 1 3 10 30 100 300 1000 3000 Competing Drug concentration (nM) % Specific 3H-GABA Binding Baclofen Muscimol THIP Glutamate X GABA...
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quiz4d - site. 2. GABA binds to both B and M receptor...

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